toro1Gollum, are you secretly me?For about 3 years now I've been planning a twin VFR-engined, twin supercharged Mini, with a curb weight around 1000lbs and packing at least 600hp. Ever since I was on the Formula SAE team at college, I've wanted to build a car of my own that would perform in the same way, but with the ability to blast around on public roads. There is just nothing like being able to turn as hard & as fast as you can at 60mph without even so much as tire squeal.
Remember that the VFR800 powerplant is actually 90º -- it's the RC45 that has a 180º crank. Unless you make a custom crank for this engine, you won't get it to sound like a Ferrari.
As far as power is concerned, I don't advertise this, but I've seen 167hp at the wheel on my supercharged setup -- that's right around 190hp at the crank. There's no doubt in my mind that the stock internals can handle 200+hp. With the Mini project, I was planning on running forged pistons & rods, and also adding an intercooler, and then 300hp per engine should be cake with pump gas.
BTW, I love the LS1s as well, and plan on doing the E36 M3 swap in the next few years.
Good luck with your project.
I don't think I'm you, though I just finished watching "The Prestige" which has me wondering...
I have no intentions of starting an argument, lets just get to the bottom of this like civilized adults shall we? By judging from the firing pattern listed in the FSM for the VFR800 02-05, and the degrees of rotation between fires, I'd say it's a guaranteed flat plane crank. And as I've stated, getting a Ferrari firing pattern IS definitely doable, which is impossible without a flat crank design.
These are pictures taken from the FSM's crankshaft section:
[image: crank1.jpg]
[image: Crank2.jpg]
If the crank were indeed NOT a flat design, it probably would be a 360 degree design, giving each cylinder it's own journal. Honda did this with their larger displacement V4 cruiser, name of which escapes me right now. THAT V4 sounds smooth as silk, not burly and muscular like the VFR, which is around half the displacement. As you most definitely know, it comes down to the firing pattern. The VFR engine is running as an incomplete flat V8 already, and ends up firing nothing close to symmetrical. It fires both cylinders on one bank, then the next two on the other bank, this is the only way to achieve a decent spread firing pattern on a V4 engine with a flat crank.
Firing patter and spacing:
1 - 180Degrees - 3 - 270Degrees - 2 - 180Degrees - 9 - 90Degrees (back to 1)
The cylinder numbering has odd on one side, even on the other.
The 270 and 90 degree separations are what's giving the engine it's rough sound, extremely different from the domestic V8 engines these V4's sound is commonly compared. A domestic's rough sound is created by the fact the engine is firing unevenly. It fires evenly until it burps, two cylinders on the same bank fire back to back without the other bank firing, then it's even, then it burps again, the other bank has two sequential fires as well.
The domestic V8 can "theoretically" achieve a flat crank sound with 180 degree heads, that correct the exhaust pulses, but in theory, practice and theory are the same, but in practice they're not. No matter how good the exhaust will sound, the engine itself has it's inherent nature already determined by the crank. No matter how loud the exhaust, the sound of the engine itself is off.
I think of the rough sound of the V4 to be more like a odd fire V6, a V6 design that only has 3 rod journals, that have to be shared. If this is a 90 degree block design then the firing pattern won't be even. If it's a 60 degree design, the pulses will be even. The odd fire V6 doesn't have nearly the same gaps as the V4, but the characteristics are very similar.
You can hear the roughness of the odd fire V6 here:
[video: https://www.youtube.com/embed/zw1e-Ge5-Cw?feature=oembed]
The big difference between an odd fire engine, and a domestic V8, is that the V8's roughness will be linear. As the engine gets louder, the roughness is still just as noticeable. With a odd fire engine, as the RPM's increase, the difference in the firing time difference decreases, and the rough nature becomes harder and harder to hear among the other engine noises. This should be easily perceived by any of you VFR owners.
If I'm completely wrong, which is possible, please let me know why. I'm 100% all ears.
Now onto other things.
As far as turbo plumbing goes, I plan to run one close to equal length header for each side, not engine. So each engine will share both turbos. I'm still undecided if I want to feed the turbos to the engines separately or together. I might feed them both into a common intercooler, and then split the air to both engines. The only reason I'd want to split them, is because designing an intake plenum that's shared might end up being HUGE depending on how far apart the engines have to be. If I can get them within 6 inches or so, then a common plenum should be doable, if not then I'll have to build a plenum for each engine, and do my best to create equal flow with balance tubes.
I hope to use the stock velocity stacks as I think they're a wonderful design for an OEM piece, and just enclosing them in a good size plenum should be sufficient.
What will be more interesting will be the intercooler/radiator setup. I'm still undecided, but there's so much room in the Z engine bay that there's no point in putting the radiator TWO FEET from the engine. Let me dig up some examples of what I've been considering as inspiration.
Here's a Z guy I really respect, known as "blueoval Z" on our message boards. He's running a small block ford.
[image: blueoval.jpg]
[image: hoodoff002.jpg]
In my case, the engine should be considerably more compact, even with the gap between them. I'm thinking I'll rake the radiator forward like he did, but set it farther back, and build a duct for it from the front, and curve the duct towards the hood, and run the intercooler as the exit for the duct, and make the intercooler a "shaker hood" type setup. This should give the intercooler decent flow and keep plumbing length to a minimum. It will also keep weight close to the wheel centerline, not way off the nose. This engine combo should be light, but I'll also be running without a transmission in the tunnel, so I'll be removing quite a bit of weight from the rear. I have to consider many aspects about the weight reduction I'll be doing in order do this right.
Oh, and I don't mind the slight offshoot topics started here. They're all interesting, and somewhat related I think. I'm enjoying it, so as long as the mods don't care, share away...
And back to the LS1 real quick. I just wanted to add that the valvetrain out there to run a pushrod V8 to 10k isn't THAT expensive, it WILL induce massive camshaft wear when compared to factory. Though if you're running those kind of RPM odds are you're ok with checking your valve clearance once a month or so. 8k is the reasonable limit for reliably, beyond that you start getting diminishing returns that will create race like wear issues.
Edited August 30, 2009 by Gollum